1. Field of the Invention
The present invention relates to a powder supply method in cladding, e.g., a powder supply method in cladding in which a machining part of a workpiece is irradiated with a laser beam and powder such as powder metal is discharged to a laser applied part of the machining part so as to form a clad layer in the machining part.
2. Description of Related Art
For example, in order to improve durability of a valve seat of a cylinder head for an engine and to increase its design flexibility, such laser machining has been known that a laser beam is applied to the valve seat while a powder-shaped (powdery) cladding material is supplied thereto, and the valve seat is rotated relative to the laser beam so as to form a clad layer. The laser machining is a technique in which: the cylinder head is subjected to machining necessary for a combustion chamber of the engine, e.g., a valve-hole forming machining or the like; and laser irradiation is performed on the cylinder head while the powder-shaped cladding material having abrasion resistance and made of copper alloy or the like is supplied to that region of the cylinder head which is to be a valve seat, so as to form a ring-shaped clad layer, namely, a clad bead part to become a valve seat eventually. The technique is generally called laser clad machining or cladding.
In the meantime, quality of a product subjected to the cladding depends on a supply amount of the cladding material to a nozzle during the cladding. Accordingly, in this field, it is desired to uniformly maintain a supply amount of the cladding material (powder), particularly, a supply amount of the powder to be supplied to a filling region for each of a plurality of discharge openings provided in a nozzle.
In order to deal with such a demand, Japanese Patent Application Publication No. 2005-219060 (JP 2005-219060 A) describes a conventional technique to perform cladding by use of the aforementioned powder cladding nozzle.
The conventional technique described in JP 2005-219060 A is as follows: a powder supply device is configured such that powder metal sent out by carrier gas from a powder (powder metal) source (hereinafter referred to as a feeder) is sequentially and evenly divided by branching means such as a tee provided in the middle of a feeding passage, so that the powder metal is filled into respective filling regions of a powder cladding nozzle that is divided into four parts by a dividing portion. The powder metal is filled thereto through four supply passages. In the powder supply device, feeding distances from an outlet of the feeder to respective supply passages of the powder cladding nozzle are the same.
In the conventional technique described in JP 2005-219060 A, the feeding distances of supply paths through which the powder is supplied to the respective filling regions of the powder cladding nozzle are set to the same with respect to the respective filling regions, thereby making it possible to perform cladding by simultaneously discharging the powder from the respective filling regions to the machining part.
However, as described in the conventional technique described in JP 2005-219060 A, even if the supply paths through which the powder is supplied to the respective filling regions of the powder cladding nozzle are set to have the same feeding distance and the powder is simultaneously discharged to the machining part from the respective filling regions, it is difficult to uniformly maintain supply amounts of the powder to be supplied to the respective filling regions of the powder cladding nozzle. This causes unevenness in a clad layer formed by cladding, which may make it difficult to stabilize quality of the clad layer, eventually, quality of a product on which the cladding is performed.